The research includes 26 projects under the following general headings: Section A: Effect of hemopoietic and lymphoid organ stroma on stem cell differentiation (immunohematology) - 5 projects. Section B: In vitro hemopoietic colony formation - 4 projects. Section C: Genetic resistance to bone marrow transplantation -4 projects. Section D: Attempted in vivo spleen colony formation with human cells - 4 projects. Section E: Prevention of graft versus host disease - 9 projects.